The importance ofthe Anopheles vector in malaria transmission is evident in the continued efforts to limit, modify, or eliminate populations of anophelines. In our epidemiologically diverse study sites (Peru, Brazil) we will focus on the molecular ecology ofthe most anthropophilic Neotropical malaria vector, Anopheles darlingi, and, identify additional local/regional vectors that our preliminary data suggest are important. We hypothesize that in the mining sites aroimd Puerto Maldonado in SE Peru, and in the new agricultural settlement, Remansinho, Acrelandia, as deforestation increases, so will the importance of An. darlingi in transmission and maintenance. This has not previously been carefully monitored, except along the Iquitos-Nauta HW, and we anticipate providing up-to-date risk assessment of each ofthe localities where we will work. The identification of adult female mosquitoes using standard keys is problematic, and PCR-ITS2-RFLP assays have been implemented on a local scale aroimd Iquitos. We will expand these assays to include our study sites in SE Peru and Acrelandia. Accurate species identification will provide information on changes in species composition over time, which also might alter risk of transmission. Using microsatellite markers that we have in hand (for An. darlingi) or will develop (for other local/regional vectors) we will test for changes in genotype, population structure and evidence of expansion, particularly in the most modified sites (mining, agriculture). An. darlingi is diverging into northem and southem lineages that we detected with the nuclear white gene. We developed a diagnostic PCR-RFLP assay to survey An. darlngi to determine the lineage distributions, because genetic differentiation could signify differences in vector competence, ecology or behavior. As bednets or ITNs become more acceptable, in some situations nets alone may provoke a behavioral change in the biting times of vector species, and the ITNs can influence levels of mosquito insecticide resistance. We will monitor peak biting times, biting rate, insecticide resistance, and changes in genetic diversity and effective population size to provide baseline data for evaluation, data that are currently unavailable in most ofthe Amazon. We will use a newly developed mosquito trap that reduces risk to collectors.